The present invention relates generally to controller assemblies, such as those used in a programmable logic controller (PLC) system, and particularly to a floating connector system that facilitates attachment and detachment of individual modules, such as I/O modules, processor modules, communication modules and power supplies.
Programmable logic controllers are used throughout industry to control and monitor a wide range of machines and other movable components and systems. Conventional PLC systems utilize a plurality of modules, e.g. input/output modules, that are mechanically mounted in a rack system and electronically connected along a back plane. The individual modules can be interchanged or replaced by disconnecting them from the rack and/or back plane. It would be advantageous to eliminate the mounting components, e.g. rack and back plane, and to provide modules that were in an interlocking, modular form.
At least one attempt has been made to construct modules that may be interconnected to each other without the use of a rack or back plane. In this particular embodiment, each module includes a stationary plug and a stationary plug receptacle designed for mating engagement with the stationary plug of a next adjacent module. Additionally, each module includes a housing having a plurality of tongs on one side and a plurality of openings on the opposite side to receive the extended tongs of the next adjacent module. Each module also includes a mounting mechanism for mounting along a DIN rail.
Thus, an individual module can be attached to an adjacent module by moving the individual module along the DIN rail until the tongs and plug connector engage the openings and plug connector of the next adjacent module. Once engaged, locking mechanisms are used to hold the module prongs within the corresponding openings of the next adjacent module.
This configuration does not permit mechanical interlocking of adjacent modules independent of forming an electrical connection between modules. Additionally, the design does not permit the removal of an individual module that is sandwiched between adjacent modules without upsetting the mounting of additional I/O modules. The mechanical interlocking system requires that a module be moved laterally sufficiently far to clear its engagement prongs from the openings of the next adjacent module. To permit this lateral movement, all of the modules positioned on one side of the subject module must be moved to provide sufficient clearance for removal and/or insertion of the subject module. Once the subject module is engaged, the string of modules moved out of the way must be reengaged.
Existing modules can also suffer from vibration that commonly exists in industrial environments. Typically, one module is electrically connected to another module by mating male and female plugs. This relatively rigid connection can induce vibration from one plug connector to the next as the modules are exposed to vibrational forces in an industrial environment. Over time, this can lead to fatigue and failure of the electrical connections.
It would be advantageous to have a compact, rackless, modular PLC system utilizing modules that could be selectively, mechanically interlocked and yet readily inserted or removed regardless of whether the module was disposed between adjacent modules. It would also be advantageous to protect the electrical coupling of adjacent modules from detrimental effects of vibration.
The present invention features a programmable logic controller system. The system comprises first module having a first electrical plug connected thereto. The system also includes a second module that may be mounted adjacent the first module. The second module includes a second electrical plug connected thereto and configured to matingly receive the first electrical plug. At least one of the first and second electrical plugs is connected to its corresponding first or second module by a floating connection.
According to another aspect of the invention, a control system module is provided. The module is configured for mounting along a common mounting structure adjacent other control system modules. The system includes a housing having a back portion, a front portion, a left side and a right side. The system also includes at least one printed circuit board mounted at least partially within the housing. An attachment mechanism is configured to mount the housing to the common mounting structure, such that the back portion lies adjacent the mounting structure. Additionally, a plurality of interconnection features are arranged to permit sliding engagement of the module with a pair of adjacent PLC modules that are connected to the same mounting structure. Each module includes a pair of plug portions that are electrically coupled to the at least one printed circuit board. The plug portions are configured for engagement with a corresponding plug portion of an adjacent module. At least one of each pair of plug portions is connected to the printed circuit board by a floating connection to protect the various electrical couplings from vibration.
According to another aspect of the present invention, a method is provided for electrically connecting a plurality of modules in a PLC system while protecting the electrical connection from vibration. The method includes aligning a first module with a second module. The method further includes affixing a first electrical plug portion to the first module, and connecting a second electrical plug portion to the second module by a flexible connector. Further, the method includes moving the second electrical plug portion into engagement with the first electrical plug portion, while the first module remains generally fixed with respect to the second module.